Enhanced Carrier Injection in AlGaN-Based Deep Ultraviolet Light-Emitting Diodes by Polarization Engineering at the LQB/p-EBL Interface

Abstract

The external quantum efficiency (EQE) of AlGaNbased deep ultraviolet light-emitting diodes (DUV LEDs) is still far from satisfactory due to the main issues of electron leakage and insufficient hole injection. The positive sheet charges generated by polarization at the interface between the last quantum barrier (LQB) and the p-type electron blocking layer (p-EBL) can induce electron accumulation and hole depletion in the vicinity of this interface, leading to electron leakage and hindering the hole injection. In this paper, we propose an Al-composition-increasing AlGaN layer (ACI-AlGaN) inserted between the LQB and p-EBL to enhance the carrier injection ability of DUV LEDs via modulating the sheet charges generated by polarization at the LQB/EBL interface and the underlying mechanism was analyzed by numerical calculation. The inserted structure can eliminate the positive sheet charges at the p-side interface of LQB and induce hole accumulation in the vicinity of the n-side interface of p-EBL, which can subsequently reduce electron leakage and favor hole injection respectively. The proposed DUV LED structure with an ACI-AlGaN layer exhibited enhanced EQE by 45.7% and its forward voltage maintained undegraded. This design scheme can provide an alternative way to promote the performance of DUV LEDs with a variety of applications.

Enhancing the Performance of GaN-Based Light-Emitting Diodes by Incorporating a Junction-Type Last Quantum Barrier

“…Consequently, it may significantly compromise both the electron blocking and hole injection processes, ultimately resulting in a diminished optical power and efficiency [22]. As a result, many strategies aimed at improving the amount of droop utilize either an Al composition gradient [23][24][25] or a final barrier with a different thickness [23,26,27] as a workaround for this issue. In a previous study we reported high−performance green LEDs employing heterojunction−type last quantum barrier layers [28].…”

Research Progress of AlGaN-Based Deep Ultraviolet Light-Emitting Diodes

“…Recently, Liu et al studied the hole injection at the last quantum barrier (LQB) and p-EBL interface. By inserting an Al-composition-increasing AlGaN layer (ACI-AlGaN) between the LQB and p-EBL, the effective barrier height of holes could be reduced, and the hole accumulation could be induced in the vicinity of the n-side interface of the p-EBL, so as to promote hole injection and improve the EQE and optical power of the DUV LEDs [49].…”